scholarly journals Biochemical limits to microbial growth yields: An analysis of mixed substrate utilization

1989 ◽  
Vol 33 (6) ◽  
pp. 799-799 ◽  
Author(s):  
P. J. F. Gommers ◽  
B. J. van Schie ◽  
J. P. van Dijken ◽  
J. G. Kuenen
Keyword(s):  
Microbial Growth ◽  
Substrate Utilization ◽  
Growth Yields ◽  
Mixed Substrate

Biochemical limits to microbial growth yields: An analysis of mixed substrate utilization

1988 ◽  
Vol 32 (1) ◽  
pp. 86-94 ◽  
Author(s):  
P. J. F. Gommers ◽  
B. J. van Schie ◽  
J. P. van Dijken ◽  
J. G. Kuenen
Keyword(s):  
Microbial Growth ◽  
Substrate Utilization ◽  
Growth Yields ◽  
Mixed Substrate

scholarly journals Kinetics and Yields of Pesticide Biodegradation at Low Substrate Concentrations and under Conditions Restricting Assimilable Organic Carbon

2013 ◽  
Vol 80 (4) ◽  
pp. 1306-1313 ◽  
Author(s):  
Damian E. Helbling ◽  
Frederik Hammes ◽  
Thomas Egli ◽  
Hans-Peter E. Kohler
Keyword(s):  
Organic Carbon ◽  
High Performance ◽  
Microbial Growth ◽  
Substrate Utilization ◽  
Growth Yields ◽  
Bacterial Strains ◽  
High Concentration ◽  
Assimilable Organic Carbon ◽  
Low Concentrations ◽  
Substrate Concentrations

ABSTRACTThe fundamentals of growth-linked biodegradation occurring at low substrate concentrations are poorly understood. Substrate utilization kinetics and microbial growth yields are two critically important process parameters that can be influenced by low substrate concentrations. Standard biodegradation tests aimed at measuring these parameters generally ignore the ubiquitous occurrence of assimilable organic carbon (AOC) in experimental systems which can be present at concentrations exceeding the concentration of the target substrate. The occurrence of AOC effectively makes biodegradation assays conducted at low substrate concentrations mixed-substrate assays, which can have profound effects on observed substrate utilization kinetics and microbial growth yields. In this work, we introduce a novel methodology for investigating biodegradation at low concentrations by restricting AOC in our experiments. We modified an existing method designed to measure trace concentrations of AOC in water samples and applied it to systems in which pure bacterial strains were growing on pesticide substrates between 0.01 and 50 mg liter−1. We simultaneously measured substrate concentrations by means of high-performance liquid chromatography with UV detection (HPLC-UV) or mass spectrometry (MS) and cell densities by means of flow cytometry. Our data demonstrate that substrate utilization kinetic parameters estimated from high-concentration experiments can be used to predict substrate utilization at low concentrations under AOC-restricted conditions. Further, restricting AOC in our experiments enabled accurate and direct measurement of microbial growth yields at environmentally relevant concentrations for the first time. These are critical measurements for evaluating the degradation potential of natural or engineered remediation systems. Our work provides novel insights into the kinetics of biodegradation processes and growth yields at low substrate concentrations.

scholarly journals Phototrophic lactate utilization by Rhodopseudomonas palustris is stimulated by co-utilization with additional substrates

2018 ◽  
Author(s):  
Alekhya Govindaraju ◽  
James B McKinlay ◽  
Breah LaSarre
Keyword(s):  
Organic Acids ◽  
Rhodopseudomonas Palustris ◽  
Substrate Utilization ◽  
Carbon Utilization ◽  
Mixed Substrate ◽  
Metabolic Versatility ◽  
Carbon Substrates ◽  
Glycerol Utilization ◽  
Lactate Utilization ◽  
Time Frames

The phototrophic purple nonsulfur bacterium Rhodopseudomonas palustris is known for its metabolic versatility and is of interest for various industrial and environmental applications. Despite decades of research on R. palustris growth under diverse conditions, patterns of R. palustris growth and carbon utilization with mixtures of carbon substrates remain largely unknown. R. palustris readily utilizes most short chain organic acids but cannot readily use lactate as a sole carbon source. Here we investigated the influence of mixed-substrate utilization on phototrophic lactate consumption by R. palustris. We found that lactate was simultaneously utilized with a variety of other organic acids and glycerol in time frames that were insufficient for R. palustris growth on lactate alone. Thus, lactate utilization by R. palustris was expedited by its co-utilization with additional substrates. Separately, experiments using carbon pairs that did not contain lactate revealed acetate-mediated inhibition of glycerol utilization in R. palustris. This inhibition was specific to the acetate-glycerol pair, as R. palustris simultaneously utilized acetate or glycerol when either was paired with succinate or lactate. Overall, our results demonstrate that (i) R. palustris commonly employs simultaneous mixed-substrate utilization, (ii) mixed-substrate utilization expands the spectrum of readily utilized organic acids in this species, and (iii) R. palustris has the capacity to exert carbon catabolite control in a substrate-specific manner.

New insights on carbon use efficiency using calorespirometry – a bioenergetics-based model

2020 ◽  
Author(s):  
Arjun Chakrawal ◽  
Anke M. Herrmann ◽  
Stefano Manzoni
Keyword(s):  
Metabolic Pathways ◽  
Microbial Growth ◽  
Energy Content ◽  
Growth Yields ◽  
Balance Model ◽  
Organic C ◽  
Degree Of Reduction ◽  
Carbon Use Efficiency ◽  
Use Efficiency

<p>Soil organic carbon (SOC) represents both a source of energy (catabolism) and a building material for biosynthesis (anabolism) for microorganisms. Microbial carbon use efficiency (CUE) – the ratio of C used for biosynthesis over C consumed – measures the partitioning between anabolic and catabolic processes. While most work on CUE has been based on C mass flows, the role of SOC energy content, microbial energy demand, and general energy flows on CUE have been rarely considered. Thus, a bioenergetics perspective on CUE could provide new insights on how microorganisms utilize C substrates and ultimately allow C to be stabilized in soils.</p><p>The microbial growth reactions are generally associated with a negative enthalpy change, which results in heat dissipation from the system. This heat can be measured using an isothermal calorimeter, which is often coupled with respiration measurements. This coupled system allows studying energy and C exchanges, and calculating their ratio referred to as the calorespirometric ratio (CR). Here, we formulate a coupled mass and energy balance model for microbial growth and provide a generalized relationship between CUE and CR. In the model, we consider two types of organic C in soils, the added substrate (i.e., glucose) and the native SOC. Furthermore, we assume that glucose is taken up via aerobic (AE) and two fermentation metabolic pathways – glucose to ethanol (F1) and glucose to lactic acid (F2); for simplicity, only aerobic growth on the native SOC was adopted. We use this model as a framework to generalize previous formulations and generate hypotheses on the expected variations in CR as a function of substrate type, metabolic pathways, and microbial properties (specifically CUE). In turn, the same equations can be used to estimate CUE from measured CR.</p><p>Our results show that in a non-growing system, CR depends only on the rates of different metabolic pathways (AE, F1, and F2). While in growing systems, CR is a function of rates as well as growth yields for these metabolic pathways. Under purely aerobic conditions, our model predicts that CUE increases with increasing CR when the degree of reduction of the substrate is higher than that of the microbial biomass. Similarly, CUE decreases with increasing CR when the degree of reduction of substrate is lower than that of the biomass. In the case of combined metabolism – aerobic and fermentation simultaneously – CUE is not only a function of CR and the degree of reduction of substrates but also the rates and growth yields of all metabolic pathways involved. To summarize, in this contribution we illustrate how calorespirometry can become an efficient tool to evaluate CUE and the role of different metabolic pathways in soil systems.</p>

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